1. Field of the Invention
The present invention relates generally to a fabrication method for a giant magnetoresistive (GMR) sensor employed within a magnetic read head. More particularly, the present invention relates to a fabrication process for a GMR read sensor utilizing a silicon reduction process and a hydrogen reduction process to selectively deposit lead layers over longitudinal bias layers in side regions of a read sensor.
2. Description of the Related Art
Computers often include auxiliary memory storage devices having media on which data can be written and from which data can be read for later use. A direct access storage device (disk drive) incorporating rotating magnetic disks are commonly used for storing data in magnetic form on the disk surfaces. Data is written on concentric, radially spaced tracks on the disk surfaces by a write head, and is then read by a read head.
In a high capacity disk drive, a magnetoresistive (MR) read head which includes an MR read sensor is prevailing because of their capability to read data from a surface of a disk at greater linear densities than a thin film inductive head. The MR read sensor detects a magnetic field through the change in the resistance of its MR sense layer (also referred to as an “MR element”) as a function of the strength and direction of the magnetic flux being sensed by the MR sense layer.
The conventional MR sensor operates on the basis of an anisotropic magnetoresistive (AMR) effect in which the MR element resistance varies as the square of the cosine of the angle between the magnetization of the MR element and the direction of sense current flow through the MR element. Recorded data can be read from a magnetic medium because the external magnetic field from the recorded magnetic medium (the signal field) causes a change in the direction of magnetization in the MR element, which in turn causes a change in resistance in the MR element and a corresponding change in the sensed current or voltage.
Within the general category of MR sensors is the giant magnetoresistance (GMR) sensor manifesting the GMR effect. In GMR sensors, the resistance of the MR sense layer varies as a function of the spin-dependent transmission of the conduction electrons between magnetic layers separated by a non-magnetic layer (spacer) and the accompanying spin-dependent scattering which takes place at the interface of the magnetic and non-magnetic layers and within the magnetic layers. Currently GMR sensors using only two layers of ferromagnetic material (e.g., nickel-iron, cobalt-iron, or nickel-iron-cobalt) separated by a layer of nonmagnetic material (e.g., copper) are extensively used in data storage devices.
In a GMR sensor, one of the ferromagnetic layers referred to as the pinned layer, has its magnetization typically pinned by exchange coupling with an antiferromagnetic (AFM) layer (e.g., nickel-oxide, iron-manganese, nickel-manganese, iridium-manganese, or platinum-manganese) layer. The pinning field generated by the AFM layer should be greater than demagnetizing fields to ensure that the magnetization direction of the pinned layer remains fixed during application of external fields (e.g. fields from bits recorded on the disk). The magnetization of the other ferromagnetic layer, referred to as the free layer, however, is not fixed and is free to rotate in response to the field from the information recorded on the magnetic medium (the signal field). A cap layer of tantalum is typically formed over the GMR sensor for protecting it during its fabrication.
A “bottom-type” GMR sensor may be formed in a conventional fashion by initially depositing read sensor layers of Ni—Cr—Fe(3)/Ni—Fe(1)/Pt—Mn(15)/Co—Fe(1.6)/Ru(0.8)/Co—Fe(1.6)/Cu—O(2)/Co—Fe(1)/Ni—Fe(1.6)/Cu(0.6)/Ta(6) (thickness in nm) over a bottom gap layer of Al2O3. A monolayer photoresist is then formed and patterned over the read sensor layers in a central region. Ion milling is then performed to remove read sensor layers, as well as some gap layer material, in side regions. Longitudinal bias layers of Cr(22)/Co—Pt—Cr(10) and lead layers of Rh(45) are then deposited, preferably by ion beam sputtering at a normal angle for abutting the sensor at it edges. The monolayer photoresist is then removed with use of a chemical mechanical polishing (CMP) lift-off process. Thereafter, a top Al2O3 gap layer is formed over the entire read head.
There are several disadvantages of the conventional bottom-type GMR sensor and the method by which it is made, as described above. First, in order to attain a stable GMR response, the Cr film in the longitudinal bias layers must be formed thick enough to align the midplane of the Co—Pt—Cr film with that of the sense or free layers (Co—Fe/Ni—Fe) of the read sensor. When this alignment is attempted, however, the Cr film has a relatively large thickness at the contiguous junctions; this causes the Co—Pt—Cr film and the free layer to be separated, which significantly reduces the stabilization efficiency. Second, the lead layers of Rh must be formed with a relatively large thickness so that they provide a relatively low-resistance electrical path. Unfortunately, the relatively large thickness of the leads causes Rh material to form over the sides of the monolayer photoresist, which makes it difficult to remove the monolayer photoresist with the CMP lift-off process. Third, there is a concern with using a CMP lift-off process to remove the monolayer photoresist due to potential damage to the read sensor layers. As apparent, it is difficult to form both thick longitudinal bias and lead layers in achieving the above-stated advantages without having difficulties in removing the monolayer photoresist.
Accordingly, there is an existing need to overcome these and other deficiencies of the prior art.